With rapid development of lighting devices, particularly the development of LED lighting devices having high efficiency and requiring low power, various luminaires applying LED technique are widely applied to every aspect of daily life, for example, indoor lighting or public lighting. Consequently, the requirements of users on electrical performance, mechanical performance and lighting effect of LED lighting devices are increased. At the present, a PSR type LED driver circuit that works based on the phase cut dimming principle is widely applied due to the requirement of the market on product cost. Moreover, higher and higher requirements on dimming range of LED lighting devices having such a driver circuit are made by users, for example, it is required that such an LED lighting device can provide a wider dimming range, and particularly, a deep dimming is further required when said LED lighting device is regulated to the lower limit of the dimming range. Considering these requirements, improvements are provided in the prior art.
In a solution of the prior art, it is provided that an LED lighting device can have a further deep dimming in a situation of reaching the lower limit of the dimming range by adding dissipative elements, such as adding a bleeder circuit, wherein said bleeder circuit is enabled to share partial electrical energy of the whole driver circuit, so as to achieve the object of performing a deep dimming, and the dimming effect thereof is shown in FIG. 1. However, in a situation that a deep dimming might be allowed, a large quantity of unnecessary power dissipation is resulted from such a solution, which renders that a large quantity of electrical energy is consumed and wasted. Moreover, in order to achieve said object, extra dissipative elements have to be added in the circuit. In this case, not only cannot save electrical energy, but also unnecessary cost consumption is generated in such a circuit design.